metal shavings in block

[slowsport]

ok i am thinking of doing a stick coil mod to my NC35, i done a look around on the forum and the only part that i am not 100% clear is the need of the 10mm plugs. do i need to drill and tap the head to accomodate the bigger plugs or even adding heli-coil?

is the only safe way to do this mod by taking the head off to prevent shavings in the block or is there a much simplier trick i can do to do the stick coil mod?

i know this may seem a very stupid question but i still would appreciate clarity on the matter.

[Martin]

You've got to take the heads off.

[slowsport]

thanks that's what i thought but i was hoping this would of been an easier mod.

[g-force performance]

ok i am thinking of doing a stick coil mod to my NC35, i done a look around on the forum and the only part that i am not 100% clear is the need of the 10mm plugs. do i need to drill and tap the head to accomodate the bigger plugs or even adding heli-coil?

is the only safe way to do this mod by taking the head off to prevent shavings in the block or is there a much simplier trick i can do to do the stick coil mod?

i know this may seem a very stupid question but i still would appreciate clarity on the matter.

DO NOT CONVERT TO 10mm PLUGS. That's the stupidest mod you could ever do to your beautiful NC engine. Honda spent a ton of time working with NGK to get those special plugs. The reason they are 8mm plugs is so HOnda can run the biggest valves possible in the combustion chamber. Hogging the spark plug hole out only thins the material between the spark plug and the valve seat, which causes the head to CRACK!!!!!!!!! Don' even think about it. It's just begging for disaster.

As for the Stick Coil mods they should go right on top of the stock threaded post on the 8mm plugs. They might be a little floppy around the base, but it's not a real problem. The biggest problem is getting the right signal to them. A regular coil fires as a wasted-spark set-up. That means that the stick coils will fire twice as often as they were designed to. Remember, an engine that runs stick coils is generally digitally controlled to only fire on the "bang" stroke (suck, squeeze, bang, blow). A wasted-spark coil fires on the bang and the blow. They might over heat, but more importantly, they don't have as long to fully recharge.

The other problem is the front heads. Even the shortest stick coils stick up out of the head more and run into the top radiator. They barely fit, and slightly ding the fins.

I hope that helped.

Mike Norman
G-Force Engine Development
http://www.mngforce.com

[CMSMJ1]

Interesting Mike.

A fair few V4 tuning/racing people over here offer 10mm plugs as an option and as a benefit to performance.

It does seem obvious that the valve area would be compromised..so wonder what the actual benefit is?

[slowsport]

thanks for that response norman, i haven't seen anyone voice those concerns before with the valves.

so with the wasted spark concern previously mentioned is this a worthwhile mod or not?

[g-force performance]

Interesting Mike.

A fair few V4 tuning/racing people over here offer 10mm plugs as an option and as a benefit to performance.

It does seem obvious that the valve area would be compromised..so wonder what the actual benefit is?

If you watch the trends in engine design, the spark plugs keep getting smaller....and smaller....and smaller. Why? The combustion chambers keep getting smaller.....and smaller....and smaller. Why? The valves keep getting bigger....and bigger....and bigger. Why?

Simple. The bigger the valve, the better the flow at all lift ranges. Also, the bigger the valve, the lower the lift necessary to maintain the right flow into the chamber (hence better valve control at high-rpms). The only thing limiting the valve size is the bore, or actually the combustion chamber. Old-school combustion chambers have a very angled pent-roof design. Somewhere between 25-30 degrees of incuded valve angles. The newer designs are realizing that they can get more valve in the same bore/chamber by narrowing the valve angle. If you lay out the circles on paper, you will see that a larger spark plug limits the valve size in the chamber. So, by going to a smaller plug, you can fit a bigger valve.

So, what are the performance advantages of going back to a big plug? They don't produce more spark energy? They don't produce a better spark. They don't even protrude into the chamber any further than the smaller diameter plugs. There is NO performance advantage. The ONLY advantage is you can buy a 10mm plugs at a fraction of the cost of the 8mm plugs, and they are available at almost any motorcycle shop when you walk in the door. That's not ample reason enough for me to open the risk of cracked heads. Just buy the plugs and have a spare set. It's not like you replace spark plugs as often as oil, or fill with fuel. We go through maybe 2 or 3 sets a season for racing. For a street bike, maybe a set a year. Maybe.

The "Performance" angle is BS. The "Cost" angle maybe. But, not justified in my book.

Mike Norman
G-Force Engine Development
http://www.mngforce.com

[g-force performance]

thanks for that response norman, i haven't seen anyone voice those concerns before with the valves.

so with the wasted spark concern previously mentioned is this a worthwhile mod or not?

If you had a different ECU that you could program the spark curve for each cylinder (Motec, Pectel, etc.) then yes. Otherwise, not really. You'd be better off getting higher energy Dyna or Accel coils that put out more spark energy. Just make sure to run resistor wires, plugs and caps as your ECU was designed.

Mike Norman
G-Force Engine Development
http://www.mngforce.com

[slowsport]

thanks again norman, you made it crystal clear what i should do and why honda engineers make more than i do lol.

[Neosophist]

thanks for that response norman, i haven't seen anyone voice those concerns before with the valves.

so with the wasted spark concern previously mentioned is this a worthwhile mod or not?

If you had a different ECU that you could program the spark curve for each cylinder (Motec, Pectel, etc.) then yes. Otherwise, not really. You'd be better off getting higher energy Dyna or Accel coils that put out more spark energy. Just make sure to run resistor wires, plugs and caps as your ECU was designed.

Mike Norman
G-Force Engine Development
http://www.mngforce.com

Have you run any stick-coils on any of your systems? I'm interested in your points.

I run stick coils on my NC24 (which doesnt used a wasted spark design as it has 4 coils not two becuase of the 180 firing order), it also has 10mm plugs as standard and makes the same power as most standard NC30s do... I think the 8mm plugs were a bit over-kill on the 59ps NC30 engine. But anyhow

I also run stick coils on my ZXR400 which does use a wasted spark, so the coils are wired in series.

ive covered about 6000 miles on each bike since having the stick coils in (it was done on the ZXR as i needed space in there for new airbox and I did the VFR as I just had some spare

I havnt had any running problems or signs of over-heating (yet) although your concerns are potential pit-falls, whcih im curious to find out if you actually had these manifest or were just erring on a side of caution.

I havnt noticed any performance increase or decrease, but in the case of the zxr it did give me a lot more room in the engine bay (which was the idea)

So I wouldnt really recommend it as being an essential mod either, unless your craving space

Also, wouldnt running them in series divide the voltage?